Field of the Invention
The present invention relates generally to a turbocharger, and more specifically to a turbocharger with an oil-free hydrostatic bearing.
Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
A turbocharger is used to compress air supplied to an engine using a hot gas exhaust as a driving force. The engine exhaust drives a turbine that drives a compressor to supply the compressed air to the engine. The performance of the engine is increased due to the compressed air.
Prior art turbochargers require shaft support systems that use oil lubricated bearings which depend on the viscosity of the fluid to provide a hydrodynamic film in the bearing. Components on the shaft typically include a compressor rotor mounted to one end of the shaft and a turbine rotor mounted to the other end of the shaft.
During operation of the turbocharger, significant radial and axial forces are produced by the compressor and the turbine which are reacted into the housing through the radial journal and axial thrust bearings. This is typically accomplished with a pressurized oil lubrication system to both remove heat and reduce rolling resistance. For a turbocharger, the lubrication system requires an oil cooler and a pump to supply sufficient pressure to the bearings while preventing the oil from coking. If oil pressure is lost or if the oil becomes contaminated from the internal combustion (IC) engine, degradation in bearing performance due to loss of lubrication or cooling occurs, leading to catastrophic failure of the turbocharger bearing system. Some advanced high temperature turbochargers utilize an additional coolant system in the bearing housing to further reduce bearing and bearing fluid temperature in order to prevent coking of the oil. A separate bearing lubrication system also adds weight to an aircraft which is critical to such aircraft as an unmanned aero vehicle or UAV.